advanced-use-latest

title: useLatest for Stable Callback Refs
impact: LOW
impactDescription: prevents effect re-runs
tags: advanced, hooks, useLatest, refs, optimization

useLatest for Stable Callback Refs

Access latest values in callbacks without adding them to dependency arrays. Prevents effect re-runs while avoiding stale closures.

**Implementation:**

function useLatest<T>(value: T) {
  const ref = useRef(value)
  useEffect(() => {
    ref.current = value
  }, [value])
  return ref
}

**Incorrect (effect re-runs on every callback change):**

function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
  const [query, setQuery] = useState('')

  useEffect(() => {
    const timeout = setTimeout(() => onSearch(query), 300)
    return () => clearTimeout(timeout)
  }, [query, onSearch])
}

**Correct (stable effect, fresh callback):**

function SearchInput({ onSearch }: { onSearch: (q: string) => void }) {
  const [query, setQuery] = useState('')
  const onSearchRef = useLatest(onSearch)

  useEffect(() => {
    const timeout = setTimeout(() => onSearchRef.current(query), 300)
    return () => clearTimeout(timeout)
  }, [query])
}